If you're 180 degrees off you simply rotate the crankshaft one revolution. The camshaft will turn half a revolution and the timing will be right on. If you installed the distributor with cylinder number one on top dead center on the exhaust stroke, it will be off by 180 degrees. You need to have cylinder number one on top dead center on the compression stroke when you install the distributor. If you never removed the distributor you don't have to worry about that.
What do you mean "it STILL" won't start? What led you to the timing chain? Which engine do you have?